noun. a cumulus cloud at an intermediate altitude of 2 or 3 miles.
1. Noun, singular or mass One type of alto cloud is the altocumulus. 2. Coordinating conjunction Clouds may be altocumulus or cirrocumulus if they form at higher altitudes, while those that form near the ground and remain small are cumulus humilis, or fair-weather cumulus clouds. 3. Adjective Middle clouds such as altostratus and altocumulus refer to those that occur at approximately 10,000 feet.